Induction furnace



y 7, 1956 T. R. KENNEDY 2,755,326

INDUCTION FURNAC E Filed June 2, 1955 2 Sheets-Sheet l F'lql.

ox 9D F g E INVENTOR.

THEODORE R./1EN/VEDY A T TORNE) Ju y 7, 1956 T. R. KENNEDY INDUCTION FURNACE 2 Sheets-Sheet Filed June 2, 1955 05 PO Q da FT z Fig.5.

THEODORE R. KENNEDY IN V EN TOR.

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A TTOR/VEY United States Patent INDUCTION FURNACE Theodore R. Kennedy, Yardley, Pa., assignor to Ajax Electrothermic Corporation, Trenton, N. J., a corporation of New Jersey Application June 2, 1955, Serial No. 512,765

7 Claims. (Cl. 13-27) This invention relates to electric furnaces and is directed particularly to induction furnaces of the type which are tiltable about trunnions or other supports in pouring the contents from the furnace crucible.

It is usual practice in such constructions to employ an an induction coil or inductor made of hollow tubing through which water is circulated for cooling. For greatest efficiency the inductor is arranged to encircle the crucible as closely as practicable and may even, for a very large furnace, be spaced only a few inches from the crucible. The space between the crucible and inductor is firmly packed with refractory material. In some instances, the crucible or lining is actually formed in place by sintering or fusing the refractory material about a temporary form as a first charge is melted in it.

The furnace inductor usually is surrounded by a boxlike frame or housing which is provided with trunnions for tilting and the inductor turns are generally bolted securely to supports which are in turn bolted to the sides of the housing. However, with this construction, when the furnace is tilted to discharge its contents, the shifting load places a severe strain upon the housing and therefore upon the refractory, crucible or lining Which holds the molten metal. As a result, the crucible or the lining or both may shift sufiiciently to displace or fracture the relatively thin and fragile wall of the refractory packing. Any such injury to the crucible or lining not only requires costly repairs, but may result in leakage of the molten charge or perhaps even a serious explosion in the event the molten charge causes an electrical breakdown across the turns of the water cooled inductor and water is forced back into or under the molten charge. The danger of such leakage is particularly great when the furnace is designed to be operated in a vacuum, since it is then important to construct all elements of the assembly as small and light as possible and to use the least amount of refractory material in order to reduce gas accumulation and gas leakage within the vacuum shell containing the furnace parts.

In accordance with the present invention, such dangers and objections are overcome and an assembly is provided whereby the crucible or lining, inductor turns and refractory are rigidly mounted on a base and are not connected directly to the sides of the frame or housing. They therefore constitute a unit which is movable with the frame in tilting the furnace, but is not affected by any weaving or distortion of the sides of the housing. In this Way it is possible to provide a more stable support for the elements and to insure against fracture or injury to the crucible and refractory.

The principal object of the present invention is to reduce the danger of spilled or leaking metal caused by fracture of the crucible, lining or refractory parts of an induction furnace assembly.

Another object of the invention is to provide novel means for securing the inductor turns and refractory lining in place in an induction furnace assembly in a manner to prevent relative displacement thereof.

2,755,326 Patented July 17, 1956 Another object of the invention is to make a strong rigid furnace construction in which insulating inductor coil supports made of material which is fragile or weak in tension are placed in compression by tie rods which secure them and the inductor coil and refractory lining rigidly to a supporting base piece.

A specific object of the invention is to provide an induction furnace assembly with tie rods or other securing means which serve to secure the inductor and refractory parts to the base of the assembly so that a rigid, unitary structure is provided and injury to the refractory parts will not occur even though the sides of the surrounding frame or housing should be displaced or distorted when the crucible and furnace assembly are tilted.

These and other objects and features of the present invention will appear from the following description thereof in which reference is made to the figures of the accompanying drawings:

In the drawings:

Fig. l is a vertical sectional view through a typical furnace assembly embodying the present invention;

Fig. 2 is a top plan view of the construction shown in Fig. 1;

Fig. 3 is a side elevation of the furnace assembly of Fig. 1;

Fig. 4 is a front elevation of the construction shown in Fig 1;

Fig. 5 is an enlarged view, partly in section, illustrating a detail of the construction of Fig. l; and

Fig. 6 is a perspective illustrating a portion of the detail of Fig. 5.

In that form of the invention chosen for purposes of illustration in the drawings, the furnace assembly embodies a crucible 2 surrounded by a densely packed body of refractory material 4. Inductor coil turns 6 which encircle the crucible and refractory material are preferably tubular in form and are provided with connections 8 for the circulation of cooling water therethrough. Refractory cement 10 forms an outer shell for the refractory material 4 and extends into the space between the various turns of the inductor 6.

All of these elements are supported on a base 12 formed of asbestos, lumber or other strong rigid material mounted upon cross beams 16 which, as shown, are in the form of angle iron members of T-shaped cross section held in place by bolts 18 extending upward through the lower side frame members 20 at opposite sides of the usual outer box-like housing 22. A bottom plate 24 formed of fire brick or other refractory material is located upon the base 12 and supports the marginal fire brick 26 which extend upward about the lower portion of the dense refractory material 4. Asbestos or other side walls 28 extend upward about the fire brick 26 in spaced relation with respect to the inductor coil turns 6 and are held in place by the upper side frame members 30. Side plates 32 are secured to the furnace supporting framework by bolts 34 or otherwise and are provided with trunnions 36 by which the furnace assembly may be tiltably mounted in suitable bearings.

Corner members 38 are secured to the lower and upper side frame members 20 and 30, respectively, adjacent the corners of the assembly but are insulated from the side frame members to limit the current induced therein. Corner members 38 are also secured to lower cross supports 40 and upper cross supports 42 of the box-like housing.

The inductor coil turns 6 may be arranged and connected in any suitable or preferred manner, but as shown in the drawings they are arranged in a plurality of series of turns with terminal portions 44 of each series projecting to the exterior of the casing and connected to the conductors 46 and 48 by which current is supplied thereto. The terminal portions of the coils extend outward above the lower crosssupport 40 and below the upper cross support 42, whereas an assembly 50 secured on the lower cross support 40 serves as a mounting for the conductors 46 and 48. V

In order to establish a rigid assembly consisting of inductor coil turns 6, the crucible 2, and the densely packed body of refractory material 4, each turn of the coil is provided with a plurality of radially projecting bolts 52 which are brazed or otherwise fixedly secured thereto. In a preferred arrangement, the bolts 52 are located at 90 degree intervals along the coil turns to provide four bolts on each turn of the coil. Further, as shown in Figs. and 6, 'the bolts on adjacent turns of the coil may be arranged in staggered relation with respect to each other as shown in Fig. 5. Each bolt projects through one of two parallel insulating coil supports 54 and is provided with a nut 56 for securing the coil firmly to the support. A spacer 58 holds the lower ends of the coil supports 54 in spaced relation and an anchor block 61) is firmly bolted to the uppermost ends of these same supports. A tie rod 66 is threaded into the lower end of anchor block 60 and extends downward through the spacer 58 and between the radially extending bolts 52. The lower end of the tie rod 66 passes through the bottom plate 24 and base 12, and is provided with lugs 68 formed and arranged to bear against a flange of the T-shaped cross beams 16 by which the base 12 of the furnace assembly is supported.

The coil supports 54, being formed of insulating material, are generally relatively weak and not capable of withstanding the strains or tension to which they might be subjected if not suitably restrained. However, they are capable of withstanding considerable compression. Accordingly the tie rods 66 may be tightened sufliciently to place the coil supports under compression and thereby reinforce the coil supports and hold them securely and rigidly in place. Moreover the tie rods and coil supports serve to secure the coil turns,- fire brick and bottom plate to the base of the furnace assembly so as to provide a rigid, unitary construction. Furthermore, the coil turns and densely packed refractory material provide support for the crucible throughout the base and sides thereof and hold them against displacement, preventing dangerous straining of the elements upon tilting of the furnace.

The assembly preferably also is provided with a top plate 64 which is held in place by bolts 62 threaded into anchor blocks 60. However, the top plate may be removed for replacement or other reasons by removal of bolts 62 without disturbing other elements of the assembly.

Neither the top plate nor the inductor coils are connected to the side walls of the furnace frame or housing and as a result these elements are not displaced or affected by any distortion of the side walls of the frame which may take place when the furnace assembly is tilted.

The assembly thus provided may be made of relatively light weight construction so that it is ideally suited for use in furnaces designed to be operated in a vacuum. The construction further may be produced economically and yet possesses the rigidity and durability required for consistent operation with minimum danger of injury to the crucible or other elements of the assembly.

While the crucible illustrated is in the form of a separate element, it may, if preferred, be formed directly from the densely packed refractory by sintering or partly fusing the refractory about the sides of a temporary form as as first charge of metal is melted in it. Furthermore, the number and spacing of the coil supports may be varied or increased to insure rigidity in the assembly and afford the desired support for the inductor coil and crucible or lining under all conditions of use and in all positions to which the furnace may be tilted.

The form, construction and arrangement of other elements of the assembly may also be varied as desired for any particular installation while assuring rigidity and strength which will preclude shifting, cracking or damage to the refractory lining or crucible, or displacement or injury to the inductor coil. In view thereof it should be understood that the invention shown in the drawings and described above is intended to be illustrative only and is not intended to limit the scope of the invention.

I claim:

1. An induction furnace assembly comprising a crucible having an inductor coil encircling the same, a base upon which said crucible is supported, a housing connected to the base and having trunnions thereon for tilting the crucible, insulating coil supports extending parallel to the axis of said coil, cooperating means engaging the coil and supports for securing the same together, and means connected to said coil supports for holding the same in compression and serving to secure the coils to said base independently of said housing, whereby said crucible and coil will be unaffected by twisting or distortion of the frame on tilting of the crucible.

2. An induction furnace assembly comprising a crucible having an inductor coil encircling the same, a base upon which said crucible is supported,, a housing connected to the base and having trunnions thereon for tilting the crucible, bolts secured to said coil and extending radially therefrom, insulating coil supports extending parallel to the axis of said coil to which said bolts are secured, and tie rods connected to said coil supports and serving to hold the coil supports in compression, said tie rods further serving to secure the coil supports fixedly to said base independently of said housing whereby said crucible and coil will be unaffected by twisting or distortion of the frame on tilting of the crucible.

3. An induction furnace assembly comprising a crucible, an inductor coil encircling the crucible, a base sup porting the crucible and coil, means connected to the base having trunnions thereon for tliting the furnace assembly, bolts secured to said coil and projecting radially therefrom, insulating coil supports to which said bolts are connected, anchor blocks positioned adjacent the upper ends of said coil supports, and tie rods connected to said anchor blocks and to said base and serving to hold the coil supports in compression and to said base whereby the coil is fixedly secured to the base so as to prevent displacement of the coil and crucible with respect to the base on tilting of the furnace assembly.

4. An induction furnace assembly comprising a cruci-' ble, an inductor coil surrounding the crucible, a base supporting the coil and crucible, trunnions connected to said base for tilting the furnace assembly, bo-lts secured to said coil and extending radially outward therefrom at spaced points circumferentially of the coil, insulating coil supports extending parallel to the axis of the coil on the exterior thereof and engaged by said bolts, and tie rods extending parallel to said coil supports securing said supports to said base and serving to hold the coil in fixed position with respect to the base for movement therewith as a unit upon tilting of the furnace assembly.

5. An induction furnace assembly comprising a crucible, an inductor coil surrounding the crucible, a base supporting the coil and crucible, trunnions connected to said base for tilting the furnace assembly, boltssecured to said coil at spaced points circumferentially thereof, pairs of spaced parallel insulating coil supports extending parallel to the axis of the coil at a plurality of circumferentially spaced points on the exterior of the coil and having said bolts secured thereto, tie rods extending parallel to said coil supports between said pairs thereof,- an anchor block at the upper end of each of said pairs of coil supports, said block being connected to the coil supports and the upper end of the tierod, the lower.

end of the tierod being fixedly secured to' said base so as to hold the coil supports in compression and serving to secure said coil in fixed position with respect to the base for movement therewith as a unit upon tilting of the furnace assembly.

6. An induction furnace assembly comprising a crucible, an induction coil surrounding the crucible, a base formed of refractory material and supported on cross beams, means connected to said base for tilting the furnace assembly, bolts secured to said coil and projecting radially therefrom, the bolts Onadjacent turns of the coil being staggered circumferentially of the coil, circumferentially spaced pairs of parallel insulating coil supports extending parallel to the axis of the coil on the exterior thereof with the bolts on alternate turns of the coil secured to one of said coil supports of each pair and the bolts on the remaining turns of said coil secured to the other of said coil supports of each pair, anchor blocks located adjacent the upper ends of each pair of coil supports and secured thereto and tie rods connected to said anchor blocks and extending between the coil supports of each pair, the lower ends of said tie rods being connected to said cross beams and serving to hold the coil and crucible in fixed position with respect to said base for movement therewith as a unit upon tilting of the furnace assembly.

7. An induction furnace assembly comprising a crucible, an inductor coil encircling the crucible, densely packed refractory material separating said coil from the crucible and providing lateral support for the crucible, a base supporting said crucible, coil and refractory material, trunnions connected to the base for tilting of the crucible, coil supports extending parallel to the axis of the coil on the exterior thereof, means fixedly securing said coil to said coil supports, and tie rods connected to said coil supports and to said base and serving to fixedly secure the coil supports and coil to said base for movement therewith as a unit upon tilting of the crucible.

References Cited in the file of this patent UNITED STATES PATENTS 1,571,742 Steenstrup Feb. 2, 1926 1,682,388 Lincoln Aug. 28, 1928 1,683,986 Northrup Sept. 11, 1928 1,795,926 Brace Mar. 10, 1931 1,810,820 Davis et al. June 16, 1931 1,811,213 Rohn June 23, 1931 

1. AN INDUCTION FURNACE ASSEMBLY COMPRISING A CRUCIBLE HAVING AN INDUCTOR COIL ENCIRCLING THE SAME, A BASE UPON WHICH SAID CRUCIBLE IS SUPPORTED, A HOUSING CONNECTED TO THE BASE AND HAVING TRUNNIONS THEREON FOR TILTING THE CRUCIBLE, INSULATING COIL SUPPORTS EXTENDING PARALLEL TO THE AXIS OF SAID COIL, COOPERATING MEANS ENGAGING THE COIL AND SUPPORTS FOR SECURING THE SAME TOGETHER, AND MEANS CONNECTED TO SAID COIL SUPPORTS FOR HOLDING THE SAME IN COMPRESSION AND SERVING TO SECURE THE COILS TO SAID BASE INDEPENDENTLY OF SAID HOUSING, WHEREBY SAID CRUCIBLE AND COIL WILL BE UNAFFECTED BY TWISTING OR DISTORTION OF THE FRAME ON TILTING OF THE CRUCIBLE. 